1. Field of the Invention
The invention relates to limit switches, and more particularly to rotary limit switches used for controlling the operation of reversible electric motors.
II. Description of the Prior Art
Limit switches are known which include a rotatably mounted lead screw shaft and a pair of actuating discs which axially advance on the screw shaft and make selective contact with and thereby operate adjacently mounted switches. Representative examples of prior art limit switches are disclosed in the following U.S. Pat. Nos.
Miller 2,951,920; Sept. 6, 1960; PA1 Stockwell 2,964,601; Dec. 13, 1960; PA1 Schaefer 3,175,418; Mar. 30, 1965; PA1 Delaney 3,474,317; Oct. 21, 1969; PA1 Ross 3,582,629; June 1, 1971; PA1 Bur 3,714,537; Jan. 30, 1973; PA1 Dalton 3,715,530; Feb. 6, 1973; PA1 Gatland, et al 3,825,809; July 23, 1974; PA1 Day 3,984,646; Oct. 5, 1976.
It is desirable for a limit switch to be versatile enough to conform to the differing operational objectives of the diverse types of power actuated equipment which presently incorporate a limit switch function. It is also desirable to couple this versatility with simplicity of construction.
The limit switches disclosed in Miller, Schaefer, Delaney, and Gatland are to some extent versatile, in that the positions of the actuator discs can be independently adjusted along the lead screw shaft. However, the versatility of these disclosed limit switches is circumscribed by the presence of associated switch assemblies which are fixedly attached to the frame and not capable of being adjusted.
The limit switch disclosed by Stockwell includes one switch assembly which is adjustable inside a housing. However, in Stockwell, the other switch assembly is fixedly attached to the frame and immobile. Furthermore, the limited versatility of Stockwell's limit switch is overshadowed by its mechanical complexity.